1. Field of Invention
This invention relates generally to thermotherapy, and in particular to a corona discharge thermotherapy system for relieving pain and obtaining other salutary effects in which the skin surface of a living body overlying a problem region is subjected to a corona discharge beam derived from periodic bursts of radio-frequency energy whose repetition rate is at a sonic frequency.
2. Status of Prior Art
The term "problem region" as used herein refers to a set of muscles, an arthritic joint or any other region underlying the skin of a patient which is causing difficulty and which lends itself to treatment by thermotherapy.
The interior of the human body has a normal temperature level which is usually said to be 98.6.degree. F. But actually, in the course of each 24-hour period, the body temperature rises above or falls somewhat below this nominal value. Body temperature is determined by the relationship existing between the amount of heat internally generated, which depends on basal metabolism and the amount of heat escaping from the body. Additional heat is produced as a result of muscular activity, this being dissipated by an increase in radiation, conduction or evaporation from the skin surface and by more rapid and deep breathing. If the heat produced by the body surpasses heat losses therefrom, this gives rise to fever.
Medical practitioners since ancient times have known that the application of heat to the body is useful in the relief of muscle soreness and various aches and pains, as well as in the treatment of certain pathological conditions. Thus the use of heat for the treatment of arthritis and other abnormalities is now commonplace. Hot water bottles and electrical heating pads are in widespread use, not merely to provide warmth, but also to afford a degree of relief or therapy for various conditions. In applying heat to the surface of the body, one may do so by convection, by direct contact with a warmed substance; that is, by conduction, or by radiating energy into the body by means of infrared lamps.
As pointed out in chapter 10, "Therapeutic Heat" in the text Therapeutic Heat and Cold, edited by Justus F. Lehmann and published in 1982 by Williams and Wilkins, it is generally accepted that heat produces desirable therapeutic effects, for it increases the extensibility of collagen tissues, it decreases joint stiffness, and it affords pain relief. Moreover, heat relieves muscular spasms, it aids in the resolution of inflammatory infiltrates, edema and exudates, and it enhances blood flow.
The exact physiological mechanisms by which applied heat creates soothing and analgesic effects are not known. However, regardless of how heat is generated, the results within the heated tissue are essentially the same, for heat produces a rise in the temperature of the tissue with a concomitant increase in metabolism. As a consequence, there is a relative increase in the accumulation of metabolic wastes such as carbon dioxide and acid metabolites. And because heat acts as a vasodilator, this dilation results in increased local circulation and leads to improved cellular nutrition and to an enhanced exchange of wastes. Further benefits are obtained because a greater number of phagocytes and antibodies are carried by the blood into the region being heated.
A system in accordance with the invention makes use of conversive heating which involves the transformation of some other form of energy into heat. The most commonly used sources of such energy are radio waves in the short wave and the microwave bands of the electromagnetic wave spectrum, and ultrasonic energy. Shortwave diathermy uses radio waves in the 10 to 100 MHz frequency range, the human tissues being treated with high-frequency current, either by way of induction or conduction. In microwave diathermy, the frequency is usually about 2500 MHz. While shortwave diathermy tends to spread widely in the body tissues, microwaves are quasi-optical and can be focused and directed for the heating of small selective areas.
Ultrasonic therapy employes high-frequency sound waves, but this energy is selective in its heating properties. Because ultrasonic energy is reflective at interfaces in the body, in excessive dosages it may be destructive.
A system in accordance with the present invention involves a therapeutic technique in which a corona discharge beam is created by applying to a discharge electrode bursts of radio-frequency energy whose repetition rate is at a sonic frequency. Hence, of background interest are the Di Mino U.S. Pat. Nos. 3,676,633 and 3,617,684, in which a corona discharge beam is applied to a resistor in a printed circuit so as to change the ohmic value thereof. These Di Mino patents, however, have nothing to do with thermotherapy.
Of greatest prior art interest is the Di Mino U.S. Pat. No. 4,667,677, which discloses a unit for generating a corona discharge beam and for projecting this beam toward the skin surface of a living body (human or animal) overlying a problem region, the beam serving to relieve pain and gain other salutary effects. The Di Mino unit includes a radio-frequency carrier generator which is overmodulated with an audio-frequency signal to produce periodic bursts of radio-frequency energy whose repetition rate corresponds to the frequency of the signal. These bursts are stored in a tank circuit coupled to the output of the modulated radio-frequency carrier generator. Connected by a short cable to the output of the tank circuit is a hand-held discharge electrode from which is projected a corona discharge beam, the electrode being manipulated by the operator to scan the skin surface to be treated.
The discharge electrode in the arrangement disclosed in Di Mino U.S. Pat. No. 4,667,677 must be in close proximity to the tank circuit included in the energy-generating unit, for if the cable extending between the discharge electrode and the tank circuit is long, the resultant loss of energy will be such as to militate against the production of the corona discharge beam. As a consequence, the energy-generating unit which includes the tank circuit must be adjacent the patient being treated. This creates difficulties in treating a patient; for if the region to be treated is in the neck or shoulder area, the patient may then have to crouch so as to bring the area of interest next to the discharge electrode. In the Di Mino patent arrangement, because the cable between the unit and the discharge electrode is necessarily short, the operator is not free to orient the electrode with respect to any body site, but must instead position the body site so that it is adjacent to the electrode.
Another drawback of the Di Mino unit is that it runs continuously; hence there is a danger in treating a patient with a corona discharge beam that excessive heat will be induced in the problem region, and this may be injurious to the patient. While the patient will sense when the heat is excessive, he may assume that the pain which accompanies excessive heat is a normal part of the treatment and therefore fail to instruct the operator to withdraw the corona discharge beam from the skin surface. And when the patient is an animal who is being restrained, the operator may not be able to sense the animal's reaction to excessive heat.